The purpose of this investigation is to expand our knowledge of purine metabolism in the intracellular form of Leishmania donovani. The organisms will be grown in a murine macrophage cell line (J774G8). Development of the project will be similar to that done previously with the promastigote forms of L. donovani. This includes the use of radiolabeled purines to trace metabolic pathways in the intact, infected macrophages and subsequent isolation of the amastigotes by centrifugation in Purcoll. Enzymes known to be peculiar to these organisms (adenase) or enzymes which have substrate specificities found only in these organisms (adenylosuccinate synthetase with allopurinol ribonucleoside monophosphate as a substrate) will be assayed in the isolated amastigote after metabolic studies have been completed. Our previous work has shown that the growth of several African trypanosomes also can be inhibited by the pyrazolopyrimidines allopurinol and its ribonucleoside. In this respect they are similar to the leishmania. Purine metabolism in these organisms will be studied using the African trypanosome, Trypanosoma gambiense. If the metabolic patterns are similar to those in leishmania, then those enzymes known to be important in pyrazolopyrimidine metabolism in the latter will be investigated in T. gambiense.